f) Cost of maintaining discussion site. First the computer cost. Second the time labor of the moderators. Even with for-profit journals, much of the labour is f

f) Cost of maintaining discussion site. First the computer cost. Second the time labor of the moderators. Even with for-profit journals, much of the labour is free. Its based on the the pay-forward model: "I'll constructively review your paper for free hoping you'll do the same mine and others papers". But still every publisher has a paid managing editor to supervise the overall process.